As therapeutic apheresis, a blood purification procedure is known, wherein blood or blood plasma in an extracorporeal circuit is freed from pathogenic substances. A distinction is made between non-selective plasmapheresis, wherein the plasma is separated from the blood and completely substituted, and selective plasmapheresis, wherein plasma is freed from pathogenic substances by filtration or adsorption. Diseases that are treated with therapeutic apheresis are for example autoimmune diseases. The known extracorporeal blood treatment apparatuses can be used for therapeutic apheresis.
The known extracorporeal blood treatment apparatuses for apheresis comprise a unit for obtaining plasma, in particular a plasma filter, and a treatment unit for treating the obtained plasma, in particular a purification unit comprising one or more filters or adsorbers.
The plasma filter is located in the extracorporeal blood circuit of the blood treatment apparatus. A blood supply line leads from the patient to the inlet of the plasma filter and a blood return line leads from the outlet of the plasma filter to the patient, so that blood removed from the patient can be conveyed through the plasma filter. The plasma obtained in the plasma filter is then conveyed through the purification unit and the purified plasma is again fed to the patient's blood in the extracorporeal blood circuit.
Blood and plasma are conveyed by means of pumps in hose lines, which are filled and rinsed with fluid before the start of the blood treatment. The rinsing solution is collected in a collection container, in particular a bag. In order to avoid contamination by germs, the collection bag remains on the hose line system during the whole treatment, which can last for three to five hours.
In the known blood treatment apparatuses for therapeutic apheresis, the line leading away from the purification unit branches into a first line segment leading to the blood return line and a second line segment leading to the collection container. During the treatment mode, the purified plasma flows through the first line segment to the blood return line, while the second line segment is closed. In the filling and rinsing mode, on the other hand, the rinsing solution is conveyed through the second line segment into the collection bag. The fluid flow is changed over by means of a change-over clamp, into which both line segments of the line leading away from the purification unit are placed.
In the treatment mode, it must be ensured that the purified plasma does not get into the collection bag, whereas in the filling and rinsing mode it must be ensured that the rinsing solution is collected in the collection bag. Monitoring of the correct function of the change-over clamp is therefore required.
Devices for therapeutic apheresis are known, wherein a pressure and clamp test is carried out in order to establish whether the hose line is properly placed in the change-over clamp. Change-over clamps are known which comprise a safety clip, which opens when the hose line is removed or slides out. An alarm is emitted when the safety clip opens.
The monitoring of the weight of containers for making available and collecting fluids during an extracorporeal blood treatment is known, for example as described in WO 91/15253 and U.S. Pat. No. 7,686,778 B2. For example, balances are used for balancing fresh and used dialysing fluid, which is made available and/or collected in a bag. The monitoring of the level of bags is also known in order to detect when they become empty or overflow.
The invention herein is to increase further the reliability of an extracorporeal blood treatment apparatus.